Zwitterionic Phosphorylcholine-Reconfigured PAM Hydrogel Electrolyte for Stable Aqueous Zinc-Ion Batteries

Abstract Hydrogel electrolytes provide a promising route to safe and sustainable aqueous zinc-ion batteries by retaining water, regulating ion transport, and maintaining electrode/electrolyte contact. However, conventional polyacrylamide (PAM)-based hydrogels mainly rely on neutral amide groups and hydrogen-bonding networks, limiting their ability to regulate Zn2+ transport and interfacial Zn deposition under long-term or high-rate operation. Herein, zwitterionic MPC units are incorporated into a PAM matrix to construct a phosphorylcholine-reconfigured PAM + MPC hydrogel electrolyte. The polar phosphate-containing groups and zwitterionic charge centers of MPC regulate the local chemical environment, enhance water uptake/retention and mechanical deformability, and provide interaction sites for Zn2+. As a result, PAM + MPC achieves an ionic conductivity of 5.667 mS cm–1 and a Zn2+ transference number of 0.76, reducing concentration polarization and stabilizing interfacial Zn2+ transport. The regulated hydrogel electrolyte improves Zn deposition/stripping reversibility, enhances Zn//Zn cycling stability, and maintains stable Coulombic efficiency in Zn//Cu cells. It also reduces crystalline by-product formation and mitigates Zn anode surface degradation, helping extend cell lifetime by suppressing interfacial deterioration. In Zn//NH4V4O10 full cells, PAM + MPC retains approximately 190 mA h g–1 after 1000 cycles at 1 A g–1 and operates for over 5000 cycles at 5 A g–1.